Human beings have fought various viruses for thousands of years. In 412 BC, Hippocrates described a flu-like condition he called fever of Perinthus, which is believed to be the first report on influenza infections. British scientists isolated the influenza virus first in the late 1800s and the first influenza vaccine trials started in the 1930s. Since then, a lot of progress has been made. Read on to learn about the vaccines currently available on the US market and the latest research.
Different types of flu vaccines- current options in the US
All vaccines for the 2021-2022 season in the US are quadrivalent, which means they protect against two influenza A and two influenza B viruses. Based on the age and special conditions, there are a few options to choose from.
- Standard-dose flu vaccine. A few brands are available: Afluria Quadrivalent, Fluarix Quadrivalent, FluLaval Quadrivalent, and Fluzone Quadrivalent. Different brands are approved for different age groups, starting at age 6 months. These vaccines do not contain adjuvant and the virus is grown in eggs. Cautions: these vaccines are contraindicated in case of severe allergic reactions to a prior dose of a flu vaccine, or those with severe allergic reactions to vaccine components..
- Cell-based flu vaccines like Flucelvax Quadrivalent are approved for age 4 and up. As the name implies, these vaccines contain the virus grown in cell culture. The manufacturing process uses animal cells (for example from canine kidney) to grow influenza virus instead of chicken eggs. Other vaccines like rubella, chickenpox and rotaviruses use the same technology.
- Recombinant flu vaccines ( ie Flublok Quadrivalent) are approved for individuals aged 18 and up. These vaccines are created synthetically in the lab, and this technology does not involve egg-grown vaccine virus or the use of chicken eggs. They have been licensed in the US since 2013. Cautions: individuals with severe allergy to any of the ingredients from this formula should not get this vaccine.
- Live attenuated influenza nasal spray vaccine (LAIV4) is approved for people 2-49 years of age. It contains weakened, live influenza viruses. Cautions: This vaccine should not be used in pregnant women, those with allergic reactions to any flu shot taken before, children and teens who take aspirin or other related drugs (salicylates), immunocompromised, individuals who recently took antiviral medications for flu treatment, and in other special conditions. For more details, visit the CDC website.
- Flu vaccine options for adults age 65 years and up. There are few choices for this age group: high dose vaccines, egg-based vaccines, egg-based vaccines made with an adjuvant and standard-dose. Note: the role of the adjuvant is to boost the immune response.
Click here to view the list of flu vaccines available in the US, for the 2021-2022 season. Look for updates from the Centers for Disease Control and Prevention ( CDC), as they provide details yearly.
Different types of flu vaccines. Latest research, potential options in the future
Flu vaccines are updated yearly to cover the new circulating strains. Scientists also work hard to improve the vaccine supply and its effectiveness. In the past decade, there were some significant achievements made. High-dose vaccines and vaccines made with an adjuvant for individuals age 65 or older are now available on the market. Cell-based flu vaccines and quadrivalent flu vaccines had also been developed during this time.
There is a lot of work in progress. As per the CDC, long-term goals include reducing egg-based flu vaccines and using newer technologies. Another long-term goal is to create a single flu vaccine (“the universal flu vaccine”) that provides immunity for a long time, even multiple seasons, against multiple influenza viruses.
Researchers are already working on trials of a combined COVID-19 and flu vaccine for the next season. In a press release in September 2021, Moderna announced its combination vaccine candidate, called mRNA-1073. This vaccine targets key proteins from both viruses- the spike protein for Sars-Cov-2 and hemagglutinin glycoproteins for the influenza viruses. Novavax’s COVID– vaccine and NanoFlu vaccine are also now combined and under research.
The new generations, mRNA-based flu vaccines are also moving into clinical trials. According to a research paper from Journal “Nature,” there are 3 phase-1 clinical trials with Moderna, Pfizer, and Sanofi testing mRNA flu vaccines. Many more preliminary phase studies are also in progress.
Flu vaccines safety
As per CDC, the most common side effects of the flu shot include redness, soreness, and swelling at the injection. Other symptoms include mild headaches, fever, muscle aches, and low energy. Occasionally, fainting can occur. Rare side effects include allergic reactions including anaphylaxis and other severe side effects. There are special considerations for those with allergic reactions to eggs, and the vaccination should be supervised in a medical setting. Flu shots should be given only after consulting a doctor in case of history of Guillain Barre syndrome, as this can be a very rare, but possible adverse event.
While this article provides an overview of different types of vaccines, it is best to talk to a healthcare provider, review all options and see which flu shot is best for you.
